It's a great game all-in-all, but I just like to cut to the chase with constructive criticism and skip all of the compliments this game deserves, so here goes.
The missions just get so painstakingly long and repetitive, that they are only done for the long run, not for the fun. Instead of just upping the number and difficulty across the ENTIRE game, maybe something else should have been done. As for what, I'm not sure, but again, that's the only fault with this game. It is a fun, balanced, and addicting game all-around.